1. Field of the Invention
The invention relates to an electric immersion thermometer for a standing or flowing medium, in particular water. The immersion thermometer includes a mount or body, preferably in the form of a screw fitting, a tubular housing, having a temperature sensor that protrudes into the medium, is sealed into the mount and is electrically insulated from the medium, and is heat conductively connected to the medium by way of the tubular housing. The temperature sensor includes a sensor element, preferably in the form of a semiconductor, and electrical connecting lines which pass through the tubular housing to the mount.
2. Description of the Prior Art
Electric immersion thermometers are known and generally include a housing with temperature sensor inside, which is immersed in the medium and is in continuous heat-conductive communication with the medium. Such an electric immersion thermometer is disclosed in "Lueger, Lexikon der Technik, Vol. 14, Lexikon des Feinwerktechnik L-Z, DVA, Stuttgart 1969 at Thermometer and Widerstandsthermometer". An elongated rod-like sensor is contained in an insert tube of electrically insulating material which, in turn, is set in a tubular metal housing, closed at one end and anchored in the mount or body member at the other end. The insert tube terminates at the end located in the mount in a circular heat plate of electrically insulating material on which electrical terminals are arranged for the connecting lines of the temperature sensor. The sensor element of the temperature sensor may be a metal resistor with positive temperature coefficient, a semiconductor resistor with negative temperature coefficient, and a thermocouple or the like.
Owing to the tubular housing consisting of metal and because of the fact that the temperature sensor itself is again protected by an inner insert tube of electrically insulating material, the known electric immersion thermometer is especially strong mechanically. However, by virtue of this design, the conventional immersion thermometer is fairly large and rather expensive to make. Some disadvantages of this immersion thermometer are its relatively long lag time for heat transfer from the medium to the sensor element, and the rather high heat capacity of the housing, the insert tube and the temperature sensor.
In various fields of application, particularly in the field of electronic thermostats for mixing faucets and the like, there has long been a need for compact, rapid temperature response and yet economical immersion thermometers. This need is not met by the aforementioned known immersion thermometer or similar immersion thermometers. Therefore, an object of the invention is to provide a compact, economically manufactured electric immersion thermometer with extremely rapid temperature response for mixing faucets or the like.